Without adequate handling the exhaust gases from firing units of heating systems have substantial remaining heat content and contaminations polluting the environment resulting in an undesired environmental contamination, and in a serious heat loss of the heating system. Several solutions have been proposed to reduce this losses. Such a solution is the application of a condensation unit used in heating systems operated by natural gas, in which unit the steam content of the exhaust gas becomes condensed and heat recuperated by condensation can be recycled by means of a heat exchanger.
Solutions are also known comprising conducting, actually bubbling the exhaust gas through a liquid with lower temperature than gas has, thus a large part of the heat and contaminant content of the gas remains in the liquid.
Such a solution is known in the patent application JP 57120087, where the exhaust gas produced by a firing system is conducted into the lower part of a tank filled with liquid, the gas is pumped continuously from the higher part of the tank, that is the gas will be bubbled through the liquid, while a portion of the heat content of the gas remains in the liquid. A further solution disclosed in the Patent publication JP 4244590A can be considered as an improvement of above solution, in that a liquid is sprayed into the gas room above the liquid by means of nozzles resulting in a further heat recuperating and gas scrubbing effect, while the patent application GB 1447711A discloses the use of more than one liquid based on a similar operating principle. A further similar solution is disclosed in the patent publication DE 102 38 229A1. Such solutions use several but at least two electric pumps to establish a pressure difference required in the one hand for bubbling the gas and to circulate the heat exchange liquid in the other hand.
However, several problems arise in the practice of known bubbling treatment solutions of exhaust gases mentioned above, the most important of which are the existence of limits in exploiting heat contained in the exhaust gases and filtering the solid, liquid and gas contaminations carried by the gases, both becoming more and more important in view of protection of the environment.
When bubbling high temperature gases through a mass of liquid the liquid content of the gas stream increases substantially if the temperature of the liquid reaches a temperature about 40° C. (e.g. in case of water as liquid, the steam content of the gas). This excessive formation rate of steam delimits the accessible temperature of the heat receiving liquid, since a substantial part of heat energy introduced into the liquid by the gas discharges the heat exchanger as steam, in the one hand, and in the other hand the mass of liquid losing its volume requires continuous supply. The problem cannot be solved by connecting in series of several bubbling heat exchanger units, since though the subsequent bubbling unit will separate the steam developed, but the temperature of the liquid in the heat exchanger shortly becomes as high as in the preceding tank because of the great amount of heat of the steam, thus a steam development of great extent experienced also in that tank.
Our experiments showed that above solutions according to the state of the art cannot improve substantially the efficiency of heat recovery, since these devices are heated up shortly above said critical temperature and most of the heat content of the flue gas leaves as steam. In addition, their production and operating costs are considerable, firstly because of the auxiliary devices (e.g. electric pumps) applied.
In the field of filtration technique there are several devices known for filtering contaminants in the form of gases, solids and liquids of the exhaust gases. these devices generally use solid filters, but the efficiency of these filters continuously decreases because of its rapid impregnation with contaminants and cleaning the filter is a high costs incurring and complex procedure. In many cases only a complete change of the filter results in the restoration of the adequate cleaning effect.
Other substantial solution in the field of filtering is the electrostatic filtration. Known electrostatic filters, having even huge effectiveness, cannot filter all substances and are very expensive to build and use.
The bubbling process described above also has filtering possibilities of high account. However, the methods/devices of the prior art above can filter flue gases originating from firing gases, exclusively. In case of any flue gas containing solid material the devices applying solutions according to the prior art, like even bubbling, get clogged shortly, thus becoming useless these solutions cannot or almost cannot filter the solids contained in the flue gas.
Operation of devices absorbing gases (absorbers) also shows disadvantages. In many cases, these devices apply bubbling processes bubbling the gases to be absorbed vertically into the absorbent liquid by means of turbines or compressors of great power demand, thus these processes are expensive and have less efficiency because of bubbling vertically.
Considering further different filtering techniques, like atomizing scrubbers, packed absorbers, curling and rotating scrubbers, plate towers, Venturi scrubbers, it might be stated that applying/siting these devices is very expensive and/or delimited because of clogging of the filters, big sizes due to a low efficiency and/or cleaning, and/or power demand of these processes.
Therefore, the object of the invention is to overcome the disadvantages of the solutions mentioned above, providing a method and an apparatus adapted to recover the usable heat content of vapours/gases and flue gases by means of heat exchange between vapours/gases/flue gases and a heat exchange liquid at low costs and high efficiency, and in the same time to remove solids, liquids and gases from the flue gases of the firing equipment otherwise contaminating the environment, while avoiding deposition of carbon black, tar and other contaminants on the wall of the device during bubbling.
It is also an object of the present invention to enhance the efficiency of absorption of gases in liquids.
Furthermore, the object of the present invention to provide a suction effect necessary to bubbling by means of a simple, reliable solution of low power demand and noise level.